Sanyo's HD700 Xacti was the then smallest 720p camcorder in the world, and we liked it. Time's moved on and Sanyo has a new Xacti, the HD800, and it's apparently a great leap in video quality. The new cam has an 8-megapixel CMOS sensor, and shoots 720p video at 30fps in MPEG4 format. It's also got "three-dimensional…